Optical systems transmit information as optical signals through optical fiber. Optical transmission systems have come to the forefront as an important communication technology. Advances in optical fibers over which optical data signals can be transmitted, as well as techniques for efficiently using the bandwidth available on such fibers, such as wavelength division multiplexing (WDM), have resulted in optical technologies being the technology of choice for state-of-the-art long haul communication systems.
For long haul optical communications, e.g., greater than several hundred kilometers, the optical signal must be periodically amplified to compensate for the tendency of the signal to attenuate. Erbium-doped fiber amplifers (EDFAs) are one type of amplifier that is conventionally used to amplify the attenuated signals. In general, an erbium doped fiber amplifier includes a length of optical fiber doped with a few parts per million of the rare earth element erbium. The optical signal is injected into this fiber, along with light from a special “pump” laser that is designed to excite the erbium ions.
In certain situations, for an EDFA to provide optimal amplification, it is necessary to keep the length of doped fiber at a preset constant temperature. There is, thus, a need in the art for a cost effective EDFA that can maintain its erbium-doped fiber at a constant temperature.